This is not a peer-reviewed article. 5th National Decennial Irrigation CD-ROM Proceedings Phoenix Convention Center, 5 - 8 December 2010, Phoenix, AZ USA M. Dukes ed. St Joseph Mich: ASABE ASABE Publication Number 711P0810cd
An ASABE Conference Presentation Paper Number: IRR10-1044
Precision Irrigation with Wireless Monitoring and Control System Technology José L. Chávez, Assistant Professor, Civil and Environmental Engineering Colorado State University, 1372 Campus Delivery, Fort Collins, CO 80523
Francis J. Pierce, Professor, Departments of Crop and Soil Sciences and Biological Systems Engineering Washington State University, 24106 N. Bunn Rd., Prosser, WA 99350
Todd V. Elliott, President Valhalla Wireless, 507 S. Buchanan PI., Kennewick, WA 99336
Written for presentation at the 5th National Decennial Irrigation Conference Sponsored jointly by ASABE and the Irrigation Association Phoenix Convention Center Phoenix, Arizona December 5 - 8, 2010 Abstract. Continuous move irrigation systems have been modified since the 1990s to support variable rate irrigation. Most of these systems used PLC (Programmable Logic Controllers) technology but were expensive to add remote, real-time monitoring and control through wireless sensor networks and the Internet. This article presents new technology to monitor and control continuous move irrigation systems. Two different systems were developed and installed on 2 spans of a 4-span Linear Move irrigation system: a) a Single Board Computer (SBC) connected via relays to solenoid valves/spray nozzles, sensor network radios, a GPS, an Ethernet radio, and a remote server; and b) a single wire (SW) monitoring and control system that uses a five-wire conductor cable, with 2 wires to carry 24VAC power, 2 wires to support RS-485 communications signals, and one wire as a common ground. A nozzle controller interfaces the RS-485 wire and each solenoid. The ubiquitous protocol MODBUS was implemented on all controllers for receiving and transmitting information to individual controllers. One main difference between the SBC and the SW system is the significant number of wires that is reduced using the latter system. This system reduced the cost of materials significantly and cut the installation requirements to a small fraction of the previous system in which each nozzle was wired individually to a control board. Both systems can be managed through the internet by means of an applied interface program. Keywords. variable-rate irrigation, remote control, water management zones, MODBUS, RS-485, GPS The authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural and Biological Engineers (ASABE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASABE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASABE conference presentation. Irrigation Association 2010. EXAMPLE: Author's Last Name, Initials. 2010. Title of Presentation. IA10-xxxx. St. Joseph, Mich.: ASABE. For information about securing permission to reprint or reproduce a technical presentation, please contact ASABE at
[email protected] or 269-932-7004 (2950 Niles Road, St. Joseph, MI 49085-9659 USA).
Introduction Precision irrigation is used synonymously with site-specific water management and is defined by Camp et al. (2006) as the “application of water to a given site in a quantity and at a time needed for optimum crop production, profitability, or other management objective at that specific site”). The value of precision irrigation is found in its potential to increase certain economic efficiencies by optimally matching inputs to yields in each area of a field and reducing costs (Sadler et al., 2005). However, the adoption of precision irrigation in continuous move irrigation systems has been limited largely because commercially produced precision water irrigation systems and the crop production functions needed for optimization are not yet available (Camp et al., 2006). Anecdotal evidence suggests that a low return on investment (ROI) and a lack of personnel in the irrigation industry capable of servicing precision irrigation systems greatly limit its availability in the marketplace. If true, this suggests that irrigation control systems designed for ease of installation, use, and servicing would help in adoption of this technology. Perhaps this is changing as evidenced by the recent announcement by Valley Irrigation to develop and distribute variable rate irrigation (VRI) controls in collaboration with Computronics Holdings Ltd. throughout their dealer network worldwide. For continuous move or self-propelled sprinkler irrigation systems, linear move and center pivot, the first variable rate control systems were developed experimentally in the early 1990’s (Duke et al., 1992; Fraisse et al., 1992) and patented by McCann and Stark (1993). Since that time, considerable progress has been made in precision irrigation systems as summarized by Camp et al. (2006) and Sadler et al. (2007). Precision irrigation systems are also being developed in fixed irrigation systems in crops such as tree fruit (Coates et al., 2006). We developed a remote irrigation monitoring and control system (RIMCS) for continuous move irrigation systems that allowed us to vary water application rate by nozzle every minute (Chávez et al. 2010a, 2010b). Each nozzle on a linear move was controlled by a solenoid wired individually to a 32 port control board connected via an RS232 cable to a single board computer at the linear move cart. A wireless Ethernet bridge connected the on-site (cart) computer to a remote server for remote monitoring and control of the irrigation system. Variable water application was achieved by pulsing nozzles ON or OFF as a fraction of 60 s, similar in concept to what other systems summarized by Sadler et al. (2007). While the RIMCS worked well, the system was not easy or efficient to install largely because of the amount of wiring required for nozzle control. A single wire, RS-485 node system similar to that used by Perry et al. (2002) or the powerline control system of King and Wall (2005) would simplify installation and operation of a nozzle control system. The objective of this article was to present two technologies to monitor and control continuous move irrigation systems. One technology is less costly than the other. This paper describes the system and its configuration on a 2-span experimental linear move sprinkler irrigation system.
Materials and Methods Remote irrigation and control system (RIMCS): Multi-wire configuration This irrigation control system configuration consisted of four components: a remote server, a system control module, a distributed nozzle control network and a wireless monitoring network. As installed and tested (Chávez et al. 2010a, 2010b), the distributed nozzle control network consisted of 1-in Rainbird DV100 24 VAC solenoid valves (25.4 mm diameter), each wired directly to a 32 relay - 10 Amps/12 VDC - RS232 relay board controller (R3210PROXR, National
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Control Devices, LLC, Osceola, MO), installed in a waterproof enclosure, which was mounted on the cart of a four span linear move (LM) irrigation system with each span 37 m in length (Pierce Corporation, Eugene, OR), Fig. 1a. The system included a 110 VAC/24 VDC transformer, a 110 VAC/12 VDC voltage regulator, a spike bar or power surge protection, and fuses for the transformer secondary power protection. There were 12 solenoid valves controlling nozzles for each of the first two spans (a total of 24 nozzles/solenoids). The relay board was connected via a serial cable to a single board computer (SBC, Fig. 1b upper portion), (TS-5700, Technologic Systems, Fountain Hills, AZ) installed in the system control module mounted at the cart. The SBC was equipped with a 133 MHz AMD processor, running on a Linux operating system platform, connected to a transformer 110VAC/12VDC for power. The SBC run software written in C (GNU GCC compiler) that operated the control module. Also contained in the system control module was a RS232 serial port booster that compensated for the loss of power due to the length of serial cable (~ 38 m) to the relay board (Fig. 1c), a 900 MHz wireless Ethernet bridge (WEB, Fig. 1b lower left portion), modem (MHX 920 OEM, Microhard Systems inc., Calgary, Alberta, Canada), a fast frequency hopping serial radio at 230.4 kbps, and a CPAS SS100 radio (Fig. 1b lower right portion) which received data from the wireless monitoring network (Fig. 1d and 1e). A low cost GPS (16LVS, Garmin, Olathe, KS) unit was installed at the beginning of the LM close to the cart and on the system lateral, aligned with the first sprinkler/nozzle/solenoid valve (Fig. 1a upper right portion) and connected directly to the SBC. The SBC was connected to a remote server via the WEB Ethernet Bridge using the Ethernet radios connected to the SBC and the server. This configuration allowed for remote access to the SBC for monitoring and control from the Internet.
Monitoring Network The wireless monitoring network uses 900 MHz, frequency hopping, spread spectrum radios (SS100) developed by WSU-CPAS (FCC Grant Certification number RHVCPAS100; Pierce and Elliott, 2008). A set of 4 SS100 radios (REMOTES) were installed at various locations on the LM to record and transmit data on water pressure and flow rate at each of four manifolds (Fig. 1d). Another 4 REMOTES were used to record volumetric soil water content (Fig. 1e) measured with Decagon ECH2O probes (ECHO-10, Decagon Devices, Inc., Pullman, Washington, USA), a dielectric aquameter, installed at two soil depths at four different locations. A SS100 radio (ROAMER) was installed in the system control module designed to receive data from the BASE SS100 radio (a SS100 radio installed on an existing weather station tower). The BASE was programmed to acquire 1-minute data from each REMOTE and immediately transmit these data to the ROAMER in the control box. The ROAMER automatically populated a MySQL database on the SBC. Power for the BASE, the ROAMER and the REMOTES installed on the linear was provided via switching power supply connected to a 110V outlet.
RIMCS Operating System Variable water application was achieved by opening (pulsing) individual solenoid valves for some portion of a pre-selected irrigation cycle that corresponds to a target application rate. For our purposes, an irrigation duty cycle of 60 s was chosen. The system was designed to keep each valve in the system “ON” for some fraction of the 60 s irrigation cycle as defined by an “ON-TIME” map. For practical purposes, the “ON-TIME” map for a LM irrigation system was a matrix of columns that corresponded to nozzles aligned in order across the irrigation spans and rows that corresponded to the Universal Transverse Mercator (UTM) projected co-ordinate system (UTM Northing and Easting) within an irrigated field.
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(a)
(d)
(c)
(b)
(e)
(f)
Figure 1. Pierce LM cart/controller (a), RIMCS controller showing SBC, WEB and SS100 radios (b), tower 1 relay board (c), LM span 1 flow/pressure wireless monitoring (d), soil water content wireless monitoring (e), and LM span 1/tower 1 relay board to solenoid/nozzle connection. For prescription irrigation control of the LM, a map was created at the remote server and sent to the SBC in the system control module. For operational purposes, the “ON-TIME Map could be produced in real-time by a decision support system (DSS) based on site-specific information including distributed soil moisture readings, remote sensing maps of crop water use (evapotranspiration, ET), and static site properties such as terrain attributes or soil texture. In any case, the “ON-TIME” map drives the control of the nozzle application rate and is executed at the SBC in the system control module. This was achieved using a C software program operating on the SBC. The “ON-TIME” map contains the pre-defined water application rates (or depths) pattern. This file is wirelessly transferred to the SBC from the remote server computer via the WEB radio. The “ON-TIME” file can be updated at any time during the irrigation/crop season. The RIMCS system was designed to accept in-situ SBC programs and file updates using a laptop that can be connected to the SBC Ethernet hub located in the system control module. The RIMCS multi-wire configuration software can handle relay board controllers with four, eight, sixteen and thirty two relays on a single board and can accommodate a maximum of eight relay controllers. This capacity corresponds to a maximum of 256 solenoid valves that can be
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controlled individually. These technical specifications allow the RIMCS system to operate on most existing LM and CP irrigation systems. The connection to several relay board controllers is made at the RS232 serial port booster located in the system control module. The RIMCS can also integrate additional GPS units or other more precise positioning systems. Operationally, in order to deliver the distributed (zonal) pre-defined nozzle variable water application rate, the RIMCS program reads the position-based “ON-TIME” data from an ONTIME map file and sends the irrigation pattern order to the relay board controller every minute. To attribute UTM co-ordinates to every value in the ON-TIME map file, the irrigation field northern upper corner and southern lower corner UTM co-ordinates, as well as the map number of rows and columns, are specified in the configuration file. Inherent alignment errors in the linear were compensated as described by Chávez et al. (2010c). For a LM, the map has a square or a rectangle shape filled with the ON-TIME values (units in s) for the areas where irrigation is intended, and filled with zeros where not intended. The “ON-TIME” values spacing was defined as 1 m in the “ON-TIME map file” for both Northing and Easting directions. The RIMCS program instructs a given relay how many seconds to remain opened by attributing a UTM co-ordinate to the solenoid/nozzle location in the field from the most recent averaged GPS reading and by relating that UTM location to the cell co-ordinates in the “ON-TIME” map file. Once the 1-min average DGPS (Differential GPS) UTM reading was obtained, at the beginning of the LM, the reading was attributed to the first solenoid valve/nozzle (closest nozzle to the cart). The other nozzles UTM Northing position was the same as the first nozzle position while the Easting position was determined by subtracting the nozzle distance to the first nozzle. The monitoring system operated on a one minute polling time. The BASE requests data from the SS100 REMOTE radios and then transmits the data to the ROAMER connected to the SBC. A single BASE can accommodate up to 255 REMOTES. There is no limit on the number of ROAMERS since they are receivers only. Incoming data files are stored in temporary files on the SBC. Four different record types are recorded in the SBC database. The first record corresponds to data received from the SS100 roamer radio which writes, in a single table, the readings for water flow and pressure in the manifolds and soil moisture. The second record is for the GPS readings (i.e., Northing and Easting UTM co-ordinate system), the third record is for nozzle travel speed (1 Hz GPS distance readings (m) averaged over the relay update interval, which is 60 s), and the fourth record reserved for the actual executed relay/solenoid valve ontime (s min-1). A separate process in the SBC looks for the temporary files and processes them into the user-defined remote “MySQL” database (i.e., data are transmitted from the SBC to the server computer where the database is populated automatically). Data were also stored to files on the SBC compact flash card (SanDisk Extreme series, Milpitas, CA) to prevent data loss in case of internet problems. The temporary files on the SBC are deleted after being successfully inserted into the database. The cost of the hardware for the RIMC’s configuration explained above was $16,250 to control two spans (24 nozzles) and monitor flow, pressure on the manifolds as well as soil water content at four different locations.
Remote irrigation and control system (RIMCS): Single-wire configuration Our single-wire nozzle RIMCS is conceptually illustrated in Fig. 2. The concept is to control individual solenoid valves at each spray nozzle with controllers connected to a single multi-drop bus connected to a master controller. We also wanted to connect various devices to the same multi-drop bus including GPS, sensors, and radios, with all devices in the system using the same MODBUS protocol based software.
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Controller Circuit We designed a smart controller (slave) capable of communication over a RS-485 cable, with functionality for solenoid control and monitoring sensors (Fig. 3). The slave controller employs a full-wave rectifier bridge to convert the 24VAC to DC. This DC voltage is followed by a bucktype switching power supply to reduce the approximately 20 V DC to 3.3 V DC efficiently. The switching integrated circuit (IC) can handle voltage inputs up to 40 V allowing for higher transient voltages on the power supply line without damaging the circuit. The on-board Atmel (San Jose, CA) AVR ATMega-128 8-bit microcontroller is clocked at 7.3728 MHz and consumes only 10 mA during activity. An optically isolated solid-state relay is used to switch the incoming 24VAC to provide on/off control of the solenoid. The opto-isolater consumes approximately 3.3 mA while in the ON state. The microcontroller has 2 on-board UARTS (universal asynchronous receiver transmitter) for serial communications. One of the UARTS is used to interface to a RS485 driver IC. The other UART is used to interface to an optional ETEK (ETECK NAVIGATION, Taiwan) EB-85A 5Hz GPS module. The controller board also has four 10-bit A/D converter inputs and two digital input pins with interrupt capabilities. These inputs can be used to monitor pressure, flow, temperature, as well as other sensors.
Figure 2. Conceptual diagram of the MODBUS RTU, multi-drop bus irrigation control system. The upper portion of the diagram illustrates the control system and wireless interface with a remote server. The lower portion illustrates that the bus accommodates the solenoids, analog and counter devices and a GPS device and can be extended via a wireless bridge. The SBC is the main controller and the nozzle node is the nozzle controller (Pierce, 2010).
Communication Protocol MODBUS/RTU is a communications protocol developed by Modicon (North Andover, MA) and has been in service since 1979. We chose to use it for this application due to the relative ease of implementation and proven reliability. This protocol specifies a network as a single master controller with up to 247 slave controllers using an 8-bit addressing scheme. The protocol is considered stateless. A transaction consists of a master sending a single packet addressed to a slave and the addressed slave responding with an acknowledgment or error state. No response from the slave after a timeout period is considered an error, in which case the master can make a decision to re-transmit the packet. Packet framing for MODBUS/RTU is accomplished with a fixed period of silence between packets. The protocol loosely defines functions for accessing
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and modifying a slave controller’s registers which may be address-mapped as the implementer sees fit. There are functions for bit-oriented operations such as on/off states and word-oriented operations that can be used to map values such as sensor measurements, coefficients, and configuration information. Some functions are read-only while others are read-write. Several error-states may be returned by a slave indicating invalid registers, busy status, etc. The original protocol is oriented toward 16-bit word values and does not allow for access to standard 32-bit floating-point type values. Many vendors of MODBUS devices have established common methods for extending the protocol to allow for access to 32-bit value registers. We used this extended functionality to represent 32-bit floating point values for scaled sensor measurements and GPS coordinate information.
Figure 3. Nozzle node controller circuit board. Our node controllers can be assigned a MODBUS address from 1 to 247 allowing for individual control of up to 247 solenoid or devices individually or as groups on a single irrigation system. Nodes communicate at a rate of 115.2 kb s-1 and thus may be separated by up to 1200 m of wire; more than adequate given a typical pivot is approximately 400 m or less in length. Distances greater than 1200 m can be accommodated with a wireless bridge as illustrated in Fig, 2 and discussed below. A more restrictive aspect of the wire length is power-supply voltage drop over the length of the wire due to electrical resistance. The total current draw for a single controller is approximately 15 mA. In our case, total controller current requirements are approximately 0.75 A at 3.3 V. Because we used a switching power supply, the total current requirement at 20 V is approximately 125 mA. Typical holding current for a solenoid is approximately 200 mA. For a system with 48 solenoids, the current consumption would be approximately 9.6 A. Our worst case current requirement is close to 10 A at 24VAC when all solenoid are in the active state. Using 12 AWG wire, this will result in a voltage drop of approximately 8 V across the 150 m of wire. The total current requirement must also be considered when selecting the 24VAC transformer supplying the system. In order to reduce the wire size, we used 12-conductor 18 AWG wire and tied 4 conductors together for each of the
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24VAC legs similar to that described by Perry et al. (2002). This gives an effective wire gauge of approximately 12 AWG to accommodate the higher current requirement necessary to drive all of the solenoids. The common consists of two conductors tied together. The remaining two conductors were used for the RS-485 TX and RX differential signals. The MODBUS protocol stack running on the slave units is a modified version of the open-source free-MODBUS library for Atmel AVR microcontrollers. The open-source GCC 'C' compiler for AVR microcontrollers was used to generate the target firmware code. Our implementation of the protocol stack running on the slave controllers allows for turning valves on/off, pulsing valves for a specified number of ms, or a continuous on/off time pair for a variable water application rate. With an optional GPS unit connected, the slave controller can also provide information contained in the NEMA output such as latitude, longitude, elevation, and velocity as well as transformed UTM coordinates using WGS-84 datum at a rate of 5 Hz. Pressure, flow and other sensors may also be attached to individual slaves via the analog and digital input channels and read via the MODBUS protocol (Fig. 2).
Master Controller All of the slave devices on a RS-485 cable are controlled by a master controller via the MODBUS protocol. We used a Technologic Systems (Fountain Hills, AZ) model TS-7800 single board computer (SBC) as the master controller. The SBC runs the Linux operating system and provides a low-power, small form factor solution. The SBC contains a complete 'C' language development environment allowing for changes to the operating software in situ. The SBC has several optional features such as LCD display, Keypad, and PC-104 bus allowing for future upgrades to the system. The ProconX (Brisbane, Australia) FieldTalk MODBUS Master 'C' language library for Linux was chosen for the protocol stack implementation. A Lantronix (Irvine, CA) model UDS-1100 Ethernet-To-MODBUS gateway device was used to interface the SBC master to the RS-485 bus via Ethernet. This configuration allows for multiple masters to access the RS-485 bus via the MODBUS-Ethernet gateway directly on the Ethernet bus at the irrigation system or indirectly via the Wireless Ethernet Bridge (WEB). Because the MODBUS protocol is stateless, there is no problem having multiple MODBUS masters access the slave nodes simultaneously. This allows for easy implementation of remote monitoring and display of current system status and position without affecting the normal operation of the irrigation system. The master controller continuously polls slave units for GPS positional information as well as water pressure readings via the MODBUS protocol (Fig. 4). GPS readings that indicate the system is outside of the application map boundaries and water pressure readings dropping below a threshold result in all nozzles being turned off. In the case where water pressure is detected and the current location is within the defined application map boundaries, the system calculates the correct row to load from the application map. If the map row is different than the previous calculated row, then the master sends new on/off time values to each of the nozzle nodes (slaves) with a 1 s delay between each node update. The delay serves to help mitigate a “water hammer” effect caused by turning all nozzles on (or off) simultaneously. The delay also helps reduce extreme current consumption during the time that the solenoid is first switched on before reaching its holding current.
Wireless Ethernet Bridge (WEB) In order to allow remote SBC configuration and maintenance, system monitoring and control, as well as application map updates, a Microhard Systems (Calgary, Alberta, Canada) model Spectra NT 920 Wireless Ethernet bridge was installed to connect the irrigation system Ethernet bus to the nearby network. The radios operate within the 902-928 MHz ISM band using frequency-hopping spread-spectrum (FHSS) technology. The combination of operation
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Figure 4. State diagram of the MODBUS control software. frequency, FHSS, and 1 W RF output power allow for long range communications with a high level of interference immunity. To accommodate in-field, wireless laptop access we installed a Linksys wireless router. The router serves as an Ethernet hub for the multiple Ethernet connections on the irrigation system, WIFI access to the SBC and MODBUS gateway, as well as providing remote internet access for the in-field, WIFI-enabled laptop via the Ethernet bridge.
User Application Software For the application interface we updated the Java web-start-able RIMCS software. The current version of RIMCS software allows a user to define application rates for a LM system using a graphical interface (Fig. 5). Using the RIMCS software, a user first defines the irrigation coverage area, the system configuration, the travel path, the variable-rate irrigation management zones, and the desired water application rates for each zone. The software generates a water application rate file consisting of a matrix of nozzle ON-TIMES (fraction of 60 s that the nozzle is on, per location) for each nozzle (columns) for every 1 m increment (rows) along the user defined travel path. For a linear move irrigation system, the coordinate system is rectangular and no special transformation is required to model movement along the cart travel path. For a center pivot, nozzle position is modeled as a linear moving in an arc in 1 m increments, along the circumference of the pivot, based on a GPS location of the last tower and the pivot point. The resultant application map file is a matrix of 1 m increments along the circumference (rows) for each nozzle (columns). This file is sent to the SBC master controller, which then controls the irrigation event.
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Figure 5. Screen shot showing an irrigation water application map in the view page of the remote irrigation monitoring and control system (RIMCS).
Field Implementation This system was deployed on a LM irrigation system on a 2 ha field at Prosser, WA. The linear move consists of two spans 62.5 m in length with a 19.4 m overhang. Sprinkler nozzles are spaced every 3.05 m for a total of 47 nozzles, each equipped with a 10 psi pressure regulator just above the nozzle preceded by a 1-in Rainbird DV100 24 VAC solenoid valve. A flow meter and a pressure transducer were installed in the main supply line near the cart. GPS modules were installed on the cart and on the end tower. All sensors, GPS, and solenoids were connected to the single wire, multi-drop bus via a nozzle node (Fig. 6). The multi-drop bus was interfaced to the control box using equipment described earlier. The WEB connected to computer network located 300 m away from the cart. This system replaced the system reported by Chávez et al. (2010a), which required a separate wire from each nozzle connected to a 32 port control board located at a middle tower. To install the old system on this LM, it would require two 32-port control boards installed in weather proof enclosures at the two towers to accommodate 47 nozzles and 2 GPS sensors. To wire each nozzle to the control boards to either one or the other tower would require approximately 1,070 m of wire. Approximately 190 m of RS232 communication wire is needed to wire each controller to the SBC at the cart. Another 200 m of wire for power is also needed. The new system requires a single wire installed the length of the lateral that contains wires needed for power and communications; approximately 210 m. Savings in wire alone would be $3,750 at wire costs of $3.28 m-1. A nozzle node controller board is needed for each nozzle for a total of 47 nozzle node board.
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Figure 6. Illustration of the multi-drop/RTU bus for the LM irrigation system at Prosser, WA (Pierce, 2010). Both systems include the control box installed at the cart, the flow and pressure sensors, and the cart GPS so there is no comparative advantage there. The cost of materials for the new system is approximately 50% of the older system and the installation time for 1 wire for the new system versus 50 wires for the old system is all but a small fraction. Overall, the single wire MODBUS, multi-drop irrigation control system is cost efficient both in terms of materials and installation requirements. The system incorporates capabilities for sensors and wireless bridges that make it easy to extend to other applications including fixed irrigation systems and environmental monitoring.
Summary This paper describes two technologies to monitor and control continuous move sprinkler irrigation systems (e.g., linear moves and center pivots). The first technology, RIMCS multi-wire system, was based on connecting individual nozzles/solenoid valves to a relay board mounted on a span-tower. Thus, this system required extensive length of wires to connect all solenoid valves to the control system. An improvement to the RIMCS multi-wire system resulted in the RIMCS single-wire system which controls individual solenoid valves at each spray nozzle with controllers connected to a single multi-drop bus connected to a master controller. In addition, this configuration allowed connecting various devices to the same multi-drop bus including GPS, sensors, and radios, with all devices in the system using the same MODBUS protocol based software. This new configuration resulted being less costly than the multi-wire one. Savings in wire alone would be $3,750 at wire costs of $3.28 m-1. In addition, a potential benefit of installing fewer wires on the LM could be less tower tire rutting due to less weight throughout the LM spans.
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References Camp, C.R., E.J. Sadler, and R.G. Evans. 2006. Precision water management: current realities, possibilities, and trends. p. 153-183. In A. Srinivasan (Ed.) Handbook of Precision Agriculture: Principles and Applications. The Hawthorne Press, Inc., New York. Chávez, J.L., F.J. Pierce, T.V. Elliott, and R.G. Evans. 2010a. A remote irrigation monitoring and control system (RIMCS). Part A: Description and development. Prec. Ag. J. 11: 110. Chávez, J.L., F.J. Pierce, T.V. Elliott, R.G. Evans, Y. Kim, and W.M. Iversen. 2010b. A remote irrigation monitoring and control system (RIMCS). Part B: Field testing and results. Prec. Ag. J. 11: 11-26. Chávez, J.L., F.J. Pierce, and R.G. Evans. 2010c. Compensating inherent linear move water application errors using a variable rate irrigation system. Irrig Sci. 28:203–210. Coates, R.W., M.J. Delwiche, and P.H. Brown. 2006. Design of a system for individual microsprinkler control. Trans. ASABE 49(6):1963−1970. Duke, H.R., D.F. Heermann, and C.W. Fraisse. 1992. Linear move irrigation system for fertilizer management research. p.72-81. In Proc. Int. Exposition and Tech. Conf., New Orleans, 1-4 Nov. 1992. Irrig. Assoc., Fairfax, VA. Fraisse, C.W., D.F. Heerman, and H.R. Duke. 1992. Modified linear move system for experimental water application. p. 367-376.Vol. 1. In Proc. Int. Conf. Advances in Planning, Design, and Manage. of Irrig. Systems as Related to Sustainable Land Use, Leuven, Belgium. 14-17 Sept. 1992. Vol. 1. King, B.A., and R.W. Wall. 2005. Supervisory control and data acquisition system for sitespecific center pivot irrigation. Applied Engineering in Agriculture 14:135-144. McCann, I.R., and J.C. Stark. 1993. Method and apparatus for variable application of irrigation water and chemicals. U.S. Patent No. 5,246,164. September 21, 1993. Perry, C., S. Pocknee, O. Hansen, C. Kvien, G. Vellidis, and E. Hart. 2002. Development and testing of a variable-rate pivot irrigation control system. ASABE Paper No. 022290. St. Joseph, MI. Pierce, F.J., and T.V. Elliott. 2008. Regional and on-farm wireless sensor networks for agricultural systems in Eastern Washington. Comput. and Electr. in Ag. 61: 3243. Pierce, F.J. 2010. Precision Irrigation. In: Advanced Engineering Systems for Specialty Crops: A Review of Precision Agriculture for Water, Chemical, and Nutrient Application, and Yield Monitoring, Upadhyaya, S.K., Giles, D.K., Haneklaus, S. and Schnug, E. (Eds). Landbauforschung, vTI - Agriculture and Forestry Research, special issue 340. Sadler., E.J., C.R. Camp, and R.G. Evans. 2007. New and future technology. p. 609-627. In R.J. Lascano and R.E. Sojka (Ed.), Irrigation of Agricultural Crops: Second Edition. ASA, CSSA, SSSA, Madison, WI. Sadler, E.J., R.G. Evans, K.C. Stone, and C.R. Camp. 2005. Opportunities for conservation with precision irrigation. J. Soil Water Conser. 60(6):371-379.
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